Split 10 of the peppers, then remove and discard seeds; place all of the peppers in blender and cover with 1/2 cup/125 mL boiling water. Let soak until softened, 10 to 20 minutes. Add shallots, garlic, ginger and turmeric, and whirl together, scraping down side and adding a little more water if necessary, until in smooth paste.

Trim off and discard dry ends and, if dry, outer layer of lemongrass; with side of knife, smash stalks just until split but not falling apart, then cut into 2-inch/5 cm lengths.

In skillet, heat oil over medium heat; add shrimp paste (if using) and fry for 20 seconds. Add hot pepper paste; fry, stirring constantly, until mixture is dry, very fragrant and oil is just beginning to separate, 10 to 12 minutes.

Add lemongrass and onion; fry until onion begins to soften, about 3 minutes. Stir in tamarind paste, sugar, salt and 2/3 cup/150 mL water; increase heat to medium-high and bring to boil.

When mixture is boiling, add shrimp; cook, stirring, until shrimp are no longer translucent in centre, about 6 minutes.

Makes 4 to 6 servings.